The cable generally comprises a core formed from electrical and/or optical conductors making it possible to transmit energy and information between the equipment items of the sonar situated onboard the ship and the antennas. The core of the cable is generally covered with a bundle of metal wires ensuring the mechanical strength of the cable. The construction of the cable imposes upon it a minimum radius of airvature. Below this radius, unacceptable mechanical stresses occur and result in damage to these elements. The same applies for the towed antennas of linear antenna type. The winch fixed onto the deck of the ship has a reel on which the cable can be wound when the sonar is inactive and the antennas are stowed onboard the ship. The diameter of the reel makes it possible to guarantee that the wound elements are not bent by a radius less than the minimum radius of airvature.
When the towed elements are at sea, the cable is guided by the fairlead which makes it possible to secure its effective radius of airvature. During the towing, the ship can alter its speed and its heading. Other involuntary movements of the ship may occur when the sea conditions deteriorate, notably in bad weather. These movements of the ship result in a change of direction of the cable relative to the axis of the ship. To prevent changes of direction from damaging the cable, the fairlead can be fixed relative to the ship and have a trumpet form opening out toward the rear of the ship.
Moreover, in underwater acoustics, the fairlead has to be adapted to allow the antennas to be raised onto the deck of the ship. The fairlead is for example open over its top part. The ship can be equipped with an articulated arm making it possible to pass the fish over the fairlead.
The existing devices are bulky and require an actuator for the movement of the articulated arm. Furthermore, when the fish is passed over the fairlead, it is necessary to implement anti-unrigging systems in order to avoid having the cable to which the towed elements are fixed leave its housing in the fairlead.
From the patent application FR2982579, a solution is known that mitigates the abovementioned drawbacks. This solution consists in providing a fairlead formed from sectors making it possible to guide the cable in a groove. The sectors are linked to one another by articulations with a degree of freedom in rotation about axes of rotation situated in horizontal planes substantially at right angles to a direction in which the cable extends in the fairlead at the articulation. According to one embodiment, the fairlead is linked to a frame intended to be placed on a ship, by means of an articulation with a degree of freedom in rotation about an axis contained in a vertical plane at right angles to the first articulation so as to allow a great amplitude of change of direction of the cable when the ship changes heading. So as to reduce the clearance of the cable in the sector situated on the side of the winch and reduce the problems of bad winding of the turns of the cable on the reel, the second axis advantageously cuts the groove of this sector at a point where the cable is designed to enter into contact with the groove on the side of the winch. Now, in practice, a lateral clearance of the cable is noted in the sector situated on the winch side, with the formation of a lateral clearance angle between the fairlead and the winch. This clearance leads to a poor control of the winding of the turns, particularly in the case of a change of heading of the ship.
One aim of the present invention is to mitigate this drawback.